Profile : Exercising Her Versatility : MARG HELGENBERGER KEEPS HER CAREER IN SHAPE WITH TWO UPCOMING MOVIES

"I believe one of my strengths is versatility," Helgenberger says. "I want to exercise it as often as I can."

This month, Helgenberger's versatility is getting a major workout. The Emmy Award-winner, who played the cynical prostitute K.C. on ABC's "China Beach," is starring in two high-profile TV films.

First up is ABC's chilling "Stephen King's The Tommyknockers," airing Sunday and Monday. Next Tuesday and Wednesday, Helgenberger stars in the CBS fact-based thriller, "When Love Kills: The Seduction of John Hearn."

"As far as TV goes, I get offered a lot of things," says Helgenberger, battling a cold she caught from her 2 1/2-year old son, Hughie. Helgenberger is married to actor Alan Rosenberg who plays Eli on ABC's "Civil Wars" and has a cameo in "Tommyknockers."

"I get offered everything from TV movies to series, most of which I turn down," she says with a sniffle. "The stuff I end up doing, I obviously do for a reason--it's character driven. I wouldn't say the Stephen King thing so much. It's not a real flashy role, but I do go on this journey."

In "The Tommyknockers," Helgenberger plays Bobbi, a successful Western novelist, who lives in a small Maine town with her boyfriend Gard (Jimmy Smits), an alcoholic poet. While playing catch with her dog in the woods, Bobbi stumbles across a mysterious and malevolent force--after all this is Stephen King--that affects the entire town, except for Gard.

Helgenberger believes "Tommyknockers" is essentially a love story. "That's why it appealed to me," she says, grabbing a tissue off the table in her publicist's office. "It's a beautiful romance and how love ultimately conquers all. These two love each other dearly, they really do."

The "Tommyknockers" shoot was a difficult one, Helgenberger says. "It was shot in New Zealand which is so far from here and very remote," she says. The production also was plagued by rain that crippled the filming schedule.

"A lot of it was shot in the forest and there was a lot of dirt," she says. "When dirt and water get together, you have mud. There also were lots of script changes." After the first week of filming, the original director was replaced with Australian director John Powers.

"That was very difficult," Helgenberger recalls.

Working with a dog was no picnic either. "You always have to keep on your toes being with an animal," Helgenberger says. "He was a real sweet dog, but he was just so keyed to his master's orders. There was never any sense this dog was my dog. You always just have to improvise with the dog."

She ended up feeling compassion for her four-legged co-star. "He starts off as an old dog with a cataract and ends up a young pup," Helgenberger says, laughing. "So the poor dog was going through makeup changes. He actually wore a contact lens which clouded over his eye, so he didn't have it easy."

No sooner did Helgenberger return from New Zealand than she began work on "When Love Kills," in which she plays the conniving, manipulative Debbie Banister, a successful bank vice president. In 1985, Banister set up a hit man service with her lover John Hearn (Gary Cole), a highly decorated Vietnam veteran. Hearn ended up murdering three people, including Banister's husband and brother-in-law for their insurance money.

"It was just a character I couldn't refuse," Helgenberger says.

"When Love Kills" marks the first time Helgenberger has played a real person. She wasn't able to meet with Banister, who has refused to talk about the case. "There is information about her, but it is from sources other than her," she says. "All the information I have paints this woman out to be a complete sociopath and an innately evil person."

Banister pleaded no contest to conspiracy to commit first-degree murder and is serving 30 years in a Florida prison. Banister's sentence has been extended, Helgenberger says, because "there are all of these infractions against her in prison because she's been caught in all of these compromising positions. This is a woman who is a sexual being-- whatever the sex. Whatever she needs to accomplish, she will use her body for it."

And her charm. Banister, Helgenberger says, refined the art of lying. After listening to taped phone conversations between Banister and Hearn, "I could tell by the sound of her voice the way she wove this web of deceit," she explains. "She sounded very charming and very level-headed. The investigators who interrogated her all claim she is a woman who is incredibly elusive. She topped (serial killerl) Ted Bundy when it came to deception. I don't know how she lived with herself."

Helgenberger found it difficult to live with the character because she found Banister's behavior so "despicable," especially when it came to her children. "Having their father killed for a measly insurance policy," Helgenberger says. "He wasn't abusive. This is a woman who was driven solely by greed. That's all she saw."

"Stephen King's The Tommyknockers" airs Sunday and Monday on ABC; "When Love Kills: The Seduction of John Hearn" airs May 18 and 19 on CBS; repeats of "China Beach" air Saturdays at midnight on Lifetime.